The present invention relates to manufacture of filter mouthpieces, cigarettes, cigars, cigarillos or analogous rod-shaped smokers' products, and more particularly to improvements in a method and apparatus for making rod-shaped smokers' products (hereinafter called cigarettes for short) wherein the density of one or both ends of the rod-like smoke-filtering or tobacco filler exceeds the density of the major portion of the filler. Still more particularly, the invention relates to improvements in a method and apparatus for making plain or filter cigarettes with dense ends in such a way that the density of one or both ends invariably equals or closely approximates an optimum density.
The manufacturers of cigarettes prefer machines which turn out plain or filtered cigarettes wherein one or both ends of the tobacco filler contain more tobacco than the major portion of the filler. Such cigarettes are favored by consumers because tobacco shreds are less likely to escape at the ends during removal from a pack or another type of container. The escaping shreds are likely to contaminate the container, the pocket, the handbag, the floor or the furniture. Moreover, improperly filled ends of plain or filter cigarettes are likely to go up in flames when the cigarette is lighted. Still further, tobacco shreds escaping at the ends of cigarettes are likely to contaminate the packing machine. As a rule, it suffices to densify that end of a filter cigarette which is remote from the filter mouthpiece. On the other hand, and if a densification is to take place, it is preferred to densify both ends of a plain cigarette because it is equally annoying (and often even more annoying) if tobacco shreds escape at that end which is placed into the mouth.
In accordance with presently prevailing practice, cigarettes with dense ends are produced by forming a continuous tobacco stream which contains a surplus of tobacco and by thereupon trimming the stream in such a way that the portions which are to constitute dense ends contain more tobacco than the remaining portions of the resulting filler. The filler is thereupon wrapped into a continuous web of cigarette paper and the resulting rod is severed across or adjacent to the portions containing more tobacco to yield discrete cigarettes of unit length or multiple unit length.
It is already known (refer to German Offenlegungsschrift No. 2,011,933) to measure the quantity of tobacco in those portions of the filler which are to constitute dense ends of cigarettes and to utilize the results of measurements for regulation of the trimming action. A serious drawback of the just described proposal is that any adjustments in the rate of removal of tobacco in those portions which are to constitute dense ends of cigarettes necessarily entail substantial adjustments in the rate of removal of tobacco shreds from the other (major) portions of the tobacco stream. This can result in consumption of excessive quantities of tobacco and/or in unnecessary comminuting of tobacco shreds; such comminuting invariably takes place during trimming as well as when the surplus which has been removed from the stream is fed back into the distributor of a cigarette rod making machine.